Leishmania braziliensis: a novel mechanism in the lipophosphoglycan regulation during metacyclogenesis

During metacyclogenesis of Leishmania in its sand fly vector, the parasite differentiates from a noninfective, procyclic form to an infective, metacyclic form, a process characterised by morphological changes of the parasite and also biochemical transformations in its major surface lipophosphoglycan (LPG). This lipid-anchored polysaccharide is polymorphic among species with variations in sugars that branch off the conserved Gal(beta1,4)Man(alpha1)-PO4 backbone of repeat units and the oligosaccharide cap. Lipophosphoglycan has been implicated as an adhesion molecule that mediates the interaction with the midgut epithelium of the sand fly in the subgenus Leishmania. This paper describes the LPG structure for the first time in a species from the subgenus Viannia, Leishmania (Viannia) braziliensis. The LPG from the procyclic form of L. braziliensis was found to lack side chain sugar substitutions. In contrast to other species from the subgenus Leishmania, metacyclic forms of L. braziliensis makes less LPG and add 1-2 (beta1-3) glucose residues that branch off the disaccharide-phosphate repeat units of LPG. Thus, this represents a novel mechanism in the regulation of LPG structure during metacyclogenesis.     

Histoplasmosis in a Brazilian center: clinical forms and laboratory tests

Histoplasmosis, caused by the dimorphic fungus Histoplasma capsulatum, is endemic in many regions of the Americas, Asia and Africa. It has a wide spectrum of clinical manifestations, from asymptomatic infection to severe disseminated disease. A retrospective study was carried out to describe the clinical forms and assess the clinical significance of the laboratory diagnostic tests of patients with histoplasmosis during the period of July 1987 to December 2003 at Instituto de Pesquisa Clínica Evandro Chagas/ FIOCRUZ, RJ, Brazil. Seventy-four patients were included. Forty-nine percent of the cases (n = 36) occurred in HIV positive patients who presented with disseminated disease. The remaining 38 cases were classified in different clinical forms. Histoplasma capsulatum was isolated from 69.5% of the clinical specimens sent to culture. Immunodiffusion and immunoblot were positive in 72.6% and 100% of the performed tests, respectively. Histopathologic findings suggestive of H. capsulatum were found in 63.2% of the performed exams. Serology had a lower proportion of positivity amongst AIDS patients, when compared with HIV negative patients (X2 = 6.65; p lower than 0.008). Statistical differences between AIDS and non-AIDS patients were not observed with culture and histopathology. The specific role of each test varies according to the clinical form. Physicians need to know the value and limitations of the available diagnostic tests, but before that, they have to think about histoplasmosis and consider this clinical entity in their differential diagnosis.     

The altitudinal limit of Leptohyphes Eaton, 1882 and Lachlania Hagen, 1868 (Ephemeroptera: Leptohyphidae,Oligoneuriidae) in Ecuadorian Andes streams: searching for mechanisms

We explored mechanisms determining the upper altitudinal limit of ephemeropterans from two different genera: Leptohyphes Eaton, 1882 Eaton, A.E. (1882), ?An Announcement of New Genera of the Ephemeridae?, The Entomologist's Monthly Magazine, 18, 207–208. [Google Scholar] (Leptohyphidae) and Lachlania Hagen, 1868 Hagen, H.A. (1868), ?On Lachlania Abnormis: A New Genus and Species from Cuba Belonging to the Ephemerina?, Proceedings of the Boston Society of Natural History, 11, 372–375. [Google Scholar] (Oligoneuriidae). For this, we (1) surveyed the two taxa in 165 stream sites along a wide altitudinal gradient; (2) sampled benthic fauna at short altitudinal intervals along a stream, from 2780 to 3150 m above sea level; (3) collected adults at the lowest and highest sites; and (4) transplanted nymphs from the lowest to the highest study site in our stream to determine survival over time. Densities of the two taxa declined gradually with altitude and both disappeared between 2950 and 3080 m a.s.l. The upper altitudinal limit in the stream seemed to be most closely related to mean oxygen saturation, temperature, and current velocity. Adults were collected where the nymphs were found, but not at the upstream site where the nymphs were absent, implying limited upstream dispersal of adults and some of the altitudinal constraint lying at the adult stage. Short-term survival of transplanted nymphs was lower than that of controls, suggesting that the distribution was limited at the juvenile stage, and that at least some of the altitudinal constraint is related to the abiotic stream environment.     

Hypocretins: waking, arousal, or action?

The role of hypocretin (orexin) neurotransmission in waking and arousal, though of intense interest, is poorly understood. In this issue of Neuron, demonstrate that, in general, hypocretin neurons are minimally active during both sleep and quiet waking. In contrast, these neurons display robust activity during periods of alert and/or active waking.     

Pre-synaptic glycine GlyT1 transporter--NMDA receptor interaction: relevance to NMDA autoreceptor activation in the presence of Mg2+ ions

Rat hippocampal glutamatergic terminals possess NMDA autoreceptors whose activation by low micromolar NMDA elicits glutamate exocytosis in the presence of physiological Mg(2+) (1.2 mM), the release of glutamate being significantly reduced when compared to that in Mg(2+)-free condition. Both glutamate and glycine were required to evoke glutamate exocytosis in 1.2 mM Mg(2+), while dizocilpine, cis-4-[phosphomethyl]-piperidine-2-carboxylic acid and 7-Cl-kynurenic acid prevented it, indicating that occupation of both agonist sites is needed for receptor activation. D-serine mimicked glycine but also inhibited the NMDA/glycine-induced release of [(3H]D-aspartate, thus behaving as a partial agonist. The NMDA/glycine-induced release in 1.2 mM Mg(2+) strictly depended on glycine uptake through the glycine transporter type 1 (GlyT1), because the GlyT1 blocker N-[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl])sarcosine hydrochloride, but not the GlyT2 blocker Org 25534, prevented it. Accordingly, [(3)H]glycine was taken up during superfusion, while lowering the external concentration of Na(+), the monovalent cation co-transported with glycine by GlyT1, abrogated the NMDA-induced effect. Western blot analysis of subsynaptic fractions confirms that GlyT1 and NMDA autoreceptors co-localize at the pre-synaptic level, where GluN3A subunits immunoreactivity was also recovered. It is proposed that GlyT1s coexist with NMDA autoreceptors on rat hippocampal glutamatergic terminals and that glycine taken up by GlyT1 may permit physiological activation of NMDA pre-synaptic autoreceptors.     

Health-related quality of life in ADHD: a pooled analysis of gender differences in five atomoxetine trials

Attention-deficit/hyperactivity disorder (ADHD) is associated with considerable impairment in health-related quality of life (HR-QoL). Atomoxetine has been found to improve HR-QoL in both children and adolescents. However, there is scarcity of data on gender differences in treatment responses to ADHD medications. This pooled analysis of five atomoxetine trials aimed to evaluate treatment differences with respect to HR-QoL and ADHD symptoms across genders. Data from 5 clinical atomoxetine trials (4 from Europe and 1 from Canada) with similar inclusion and exclusion criteria and similar durations (8- to 12-week follow-up) were included in the pooled analysis. All studies included the Child Health and Illness Profile-Child Edition (CHIP-CE) Parent Report Form. In addition, correlations between HR-QoL and ADHD core symptoms were compared between girls and boys. Data from 136 girls and 658 boys (mean age: 9.6 and 9.7 years, respectively) were pooled. Boys and girls were similarly impaired at baseline with minor differences in some of the subdomains. Treatment effect of atomoxetine was significant in both groups for the Risk Avoidance domain and its subdomains. No gender effect with both clinical and statistical significance was found for treatment outcome. Correlations between ADHD Rating Scale and CHIP-CE scores were similar in both genders and were generally low at baseline and moderate at endpoint and for the change from baseline to endpoint. Atomoxetine was effective in improving some aspects of HR-QoL in both genders without any significant differences across genders. Correlations between core symptoms of ADHD and HR-QoL were low to moderate in both boys and girls.     

Predicting the Recovery of <Emphasis Type="Italic">Pinus halepensis</Emphasis> and <Emphasis Type="Italic">Quercus ilex</Emphasis> Forests after a Large Wildfire in Northeastern Spain

Quercus ilex and Pinus halepensis are two of the most common tree species of the western Mediterranean basin. Both species regenerate reliably after fire: P. halepensis colonizes recently disturbed areas by effective seedling recruitment, while Q. ilex resprouts vigorously after disturbances. For this reason, the natural regeneration of these species after fire should ensure the re-establishment of a forest similar to that which existed before the fire. This study analyzes with a simple simulation model whether or not the relative abundance of monospecific and mixed forests of these species in the landscape is altered by fire. We also analyze the topographic factors and the forest structure before the fire that determine the changes in forest composition after fire. This study has been carried out in a large fire that occurred in NE Spain. Overall, 33% of plots changed to another community type, but this probability of change varied considerably among community types before the fire. Monospecific forests of P. halepensis or Q. ilex had a high probability of remaining in their original composition after the fire, whereas the resilience of mixed forests of these two species was quite low. Mixed forests changed for the most part to monospecific P. halepensis or Q. ilex forests. Analysis of several factors determining these changes indicated that only elevation as a significant topographical variable. The effect of fire was to increase the altitudinal differentiation between the two species. P. halepensis forests that changed to mixed or Q. ilex forests were those of highest elevation, while the mixed and Q. ilex plots that changed to P. halepensis forests were those located at the lowest elevations. Concerning structural variables before fire, density of Q. ilex trees before the fire showed a much greater effect than P. halepensis density in determining the post-fire community. Finally, burn severity also influenced the changes observed. For both P. halepensis and Q. ilex forests, plots that changed to another forest type were mainly those that burned more severely. In the case of mixed forests, even low fire severities involved high probabilities of change to monospecific forests.     

Optimization of free fatty acid production by enzymatic hydrolysis of vegetable oils using a non-commercial lipase from Geotrichum candidum

Bioprocess and Biosystems Engineering - This study aimed to optimize free fatty acid production by enzymatic hydrolysis of cottonseed, olive and palm kernel oils in stirred-tank reactors using a...     

Physiologic and metagenomic attributes of the rhodoliths forming the largest CaCO3 bed in the South Atlantic Ocean

Rhodoliths are free-living coralline algae (Rhodophyta, Corallinales) that are ecologically important for the functioning of marine environments. They form extensive beds distributed worldwide, providing a habitat and nursery for benthic organisms and space for fisheries, and are an important source of calcium carbonate. The Abrolhos Bank, off eastern Brazil, harbors the world''s largest continuous rhodolith bed (of ∼21 000 km²) and has one of the largest marine CaCO₃ deposits (producing 25 megatons of CaCO₃ per year). Nevertheless, there is a lack of information about the microbial diversity, photosynthetic potential and ecological interactions within the rhodolith holobiont. Herein, we performed an ecophysiologic and metagenomic analysis of the Abrolhos rhodoliths to understand their microbial composition and functional components. Rhodoliths contained a specific microbiome that displayed a significant enrichment in aerobic ammonia-oxidizing betaproteobacteria and dissimilative sulfate-reducing deltaproteobacteria. We also observed a significant contribution of bacterial guilds (that is, photolithoautotrophs, anaerobic heterotrophs, sulfide oxidizers, anoxygenic phototrophs and methanogens) in the rhodolith metagenome, suggested to have important roles in biomineralization. The increased hits in aromatic compounds, fatty acid and secondary metabolism subsystems hint at an important chemically mediated interaction in which a functional job partition among eukaryal, archaeal and bacterial groups allows the rhodolith holobiont to thrive in the global ocean. High rates of photosynthesis were measured for Abrolhos rhodoliths (52.16 μmol carbon m⁻²s⁻¹), allowing the entire Abrolhos rhodolith bed to produce 5.65 × 10⁵ tons C per day. This estimate illustrates the great importance of the Abrolhos rhodolith beds for dissolved carbon production in the South Atlantic Ocean.